Distributed optical fiber sensing drainage sensing decoupling and sensitivity enhancing device and method

Abstract

The invention relates to the technical field of discharged water flow measurement, in particular to a distributed optical fiber sensing drainage sensing decoupling and sensitivity enhancing device and method.The device comprises a discharged water flow enhancing piece and a sensing piece, the discharged water flow enhancing piece comprises a flow deflector and a receiving blocking piece, the flow deflector is provided with a small collecting hole, and the receiving blocking piece comprises an elastic piece and a buckle; the flow deflectors collect and guide water flow at the discharge port to the receiving blocking pieces, after the flow deflectors are used, the water flow is concentrated through the collecting small holes and separated from the pipe wall to flow from top to bottom, gravitational potential energy of the water flow is converted into fluid kinetic energy to the maximum extent, and the fluid flowing state is converted into turbulent flow. The vibration energy of the fluid is received by the separation blade, so that the drainage water flow under the conditions of small flow and low fall can generate enough vibration so as to be sensed by the sensing piece, and the problem that the low-fall and small-flow drainage cannot be accurately sensed by a traditional drainage detection layout method based on optical fiber sensing is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring discharged water flow, and particularly to a decoupling and sensitivity enhancement device and method for drainage perception by distributed optical fiber sensing. Background Art

[0002] In the current direction of drainage monitoring, the method based on the drain outlet machine can effectively monitor existing water source points in real time. However, limited by power supply constraints, it is impossible to effectively deploy a large number of positions.

[0003] In the prior art, for example, "Monitoring of Fluid Flow in Open Channels Using Optical Fiber Sensors" disclosed in Chinese Patent Application for Invention (Publication No. CN108369118A) describes laying an optical cable at the bottom of an open channel, using optical fiber sensing technology to obtain data of strain caused by fluid-air surface waves, calculating the fluid velocity, depth, and volumetric fluid flow rate, and then controlling the flow rate by automatic components such as automatic control valves. This technology describes the monitoring method for internal flow in sewers, rivers, drainage ditches, drainage channels, and river embankments, and does not involve the flow monitoring at the drain outlet and special treatment and structural devices for the optical cable. In the prior art, for example, "Online Monitoring System and Method for Drainage Pipes Based on OFDR Distributed Optical Fiber" disclosed in Chinese Patent Application for Invention (Publication No. CN108731743A) describes laying 7 optical fibers inside the drainage pipe and attaching them to the inner wall (3 for strain + 3 for strain compensation + 1 for temperature measurement at the top), and calculating the fluid flow velocity, pipe fullness, siltation, and defects. This technology describes the monitoring of internal water flow in the pipe and does not involve the flow monitoring at the drain outlet.

[0004] Currently, the above technologies and existing drainage detection layout methods based on optical fiber sensing cannot accurately sense low-drop and small-flow drainage, and their sensitivity is poor in actual use. Summary of the Invention

[0005] The purpose of the present invention is to provide a decoupling and sensitivity enhancement device and method for drainage perception by distributed optical fiber sensing, aiming to solve the problem that the traditional drainage detection layout method based on optical fiber sensing cannot accurately sense low-drop and small-flow drainage.

[0006] To achieve the above purpose, in the first aspect, the present invention provides a decoupling and sensitivity enhancement device for drainage perception by distributed optical fiber sensing, including an enhanced component for discharged water flow and a sensing component. The enhanced component for discharged water flow includes a guide vane and a receiving baffle. The guide vane has collecting small holes, and the collecting small holes are located on one side of the guide vane. The receiving baffle is arranged on one side of the guide vane. The receiving baffle includes a spring piece and a buckle. The spring piece is arranged on one side of the guide vane, and the buckle is fixedly connected to the spring piece and is located on one side of the spring piece; The sensing component includes a laser, a beam splitter, a signal processor, and a display, and the laser, the beam splitter, the signal processor, and the display are connected in sequence.

[0007] In a second aspect, the present invention further provides a method for decoupling drainage sensing and enhancing sensitivity of distributed optical fiber sensing, which is applied to the device for decoupling drainage sensing and enhancing sensitivity of distributed optical fiber sensing as described in the first aspect above, and includes the following steps: Set the substrate parameters of the sensing component; The sensing component calculates and processes the collected signal to obtain differential phase data; Perform integral filtering processing on the differential phase data to obtain filtered data; Calculate the vibration intensity based on the filtered data within a time window; Obtain the vibration intensity value of the pipe orifice discharge based on the flow calibration result.

[0008] Among them, the basic parameters include the sampling rate, spatial resolution, channel spacing, number of sampling points, and duration to be collected.

[0009] Among them, the specific method for the sensing component to calculate and process the collected signal to obtain differential phase data: The sensing component performs synchronization processing on the collected signal to obtain processed data; Obtain differential phase data by calculating the difference between the phase data at adjacent moments of the processed data.

[0010] Among them, the method for obtaining the flow calibration result: Build an equal-size model of the drainage pipe orifice; Based on the equal-size model, change the water flow rate to obtain the corresponding vibration intensity sensed by the optical cable at the pipe orifice; Draw a scatter plot based on the positive correlation between the vibration intensity and the water flow rate; Use the least squares method to fit a parametric function; Convert the parametric function to obtain an inverse function, and calculate the corresponding water flow rate to obtain the calibration result.

[0011] The decoupling and sensitivity enhancement device for drainage sensing of distributed optical fiber sensing of the present invention. The diversion piece is used to collect and guide the water flow at the drain outlet to the receiving baffle. The diversion piece is in a funnel shape from the edge to the collection small hole. After using the diversion piece, the water flow converges through the collection small hole and detaches from the pipe wall to flow downward, so that its own gravitational potential energy is maximally converted into fluid kinetic energy (the flow velocity is increased), and the fluid flow state changes to turbulent flow. The vibration energy of the fluid is received by the baffle below the pipe orifice, so that the discharged water flow under small flow rate and low head can generate sufficient vibration to be sensed by the sensing element. The diversion piece fits the radian of the pipe orifice and is installed at the pipe orifice. The elastic piece of the receiving baffle is used to receive the vibration and transmit it to the optical cable, and is installed at a certain distance below the collection small hole of the diversion piece. The buckle is used to fix the optical cable. The sensing optical fiber (optical cable) is optically connected to the sensing element. The buckle is located on one side or the middle part of the elastic piece. The principle is that after the optical fiber is strained, the internal Rayleigh scattering changes, and the strain intensity value of the optical fiber is obtained by using the interference method. The signal processor includes a dedicated chip for processing and demodulating the optical modulation signal and an industrial control computer (computer) for general digital signal processing. The laser is the light source of the optical fiber sensor, providing coherent light and injecting it into the optical cable. The optical splitter is used to interfere the transmitted laser and the backscattered light in the optical cable in the optical path, and the phase data is obtained through the demodulation chip in the signal processor, and the current device state and data result are displayed on the display after calculation. This device selectively enhances and receives the vibration signal of the discharged water flow at the drain outlet. At the same time, through a unique optical cable coiling method, the problem of monitoring small-flow discharge outlets is solved. This device adopts a water flow enhancement piece to fully collect the water flow and maximally convert the gravitational potential energy of water into kinetic energy, and the water flow velocity is increased. According to the calculation formula of the Reynolds number , the Reynolds number is proportional to the velocity. After the Reynolds number increases, the fluid flow is less stable, and small changes in the flow velocity are prone to develop and enhance, forming turbulence, and the fluid itself has relatively large vibrations. The vibration receiving baffle is used to receive the vibration of the fluid and transmit it to the optical cable, and then a larger vibration intensity is detected at the DAS end. Moreover, the optical cable uses a new layout method at the drain outlet, and its length is at least 2 times the spatial resolution size, which solves the coupling problem between the discharge signal at the drain outlet and the flow signal in the pipe. As Figure 3 shown, the layout is divided into two types: the optical cable at the drain outlet of type I is wound around the pipe orifice and can receive the vibration signal of the drain pipe caused by the drainage at the pipe orifice; type II winds the excess optical cable on both sides of the drain outlet and is suitable for situations where the drain outlet is particularly large. During the layout process, the installation of the diversion piece can be selected. When the water volume is small enough, an additional diversion piece is installed to enhance the signal, which solves the problem that the traditional drainage detection layout method based on optical fiber sensing cannot accurately sense low-head and small-flow drainage. Description of the Drawings

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0013] Figure 1 It is a schematic structural diagram of a diversion piece of a drainage perception decoupling and sensitivity enhancement device for distributed optical fiber sensing provided by the present invention.

[0014] Figure 2 It is a schematic structural diagram of a receiving baffle of a drainage perception decoupling and sensitivity enhancement device for distributed optical fiber sensing provided by the present invention.

[0015] Figure 3 It is a schematic diagram of the optical cable layout method of the present invention.

[0016] Figure 4 It is a schematic structural diagram of a sensing component of the present invention.

[0017] Figure 5 It is a flowchart of a drainage perception decoupling and sensitivity enhancement method for distributed optical fiber sensing provided by the present invention.

[0018] Figure 6 It is a flowchart of the specific method for the sensing component to calculate and collect signals and perform processing to obtain differential phase data.

[0019] Figure 7 It is a flowchart of the method for obtaining the flow calibration result.

[0020] In the figure: 1 - diversion piece, 2 - collection small holes, 3 - elastic piece, 4 - buckle, 5 - laser, 6 - optical splitter, 7 - signal processor, 8 - display. Specific Embodiments

[0021] The following will describe in detail the embodiments of the present invention. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0022] Please refer to Figures 1 to 4, in a first aspect, the present invention provides a drainage sensing decoupling and sensitivity enhancement device for distributed optical fiber sensing, comprising a discharge water flow enhancement member and a sensing member. The discharge water flow enhancement member includes a diversion piece 1 and a receiving baffle. The diversion piece 1 has a collection small hole 2, and the collection small hole 2 is located on one side of the diversion piece 1. The receiving baffle is arranged on one side of the diversion piece 1. The receiving baffle includes a spring piece 3 and a buckle 4. The spring piece 3 is arranged on one side of the diversion piece 1, and the buckle 4 is fixedly connected to the spring piece 3 and is located on one side of the spring piece 3; The sensing member includes a laser 5, an optical splitter 6, a signal processor 7 and a display 8, and the laser 5, the optical splitter 6, the signal processor 7 and the display 8 are connected in sequence.

[0023] In an embodiment of the present invention, the diversion piece 1 is used to collect and guide the water flow at the drain outlet to the receiving baffle. The diversion piece 1 is in a funnel shape from the edge to the collection small hole 2. After using the diversion piece 1, the water flow passes through the collection small hole 2 and converges and separates from the pipe wall to flow downward, so that its own gravitational potential energy is maximally converted into fluid kinetic energy (the flow rate is increased), and the fluid flow state changes to turbulence. The vibration energy of the fluid is received by the baffle, so that the discharge water flow under small flow and low head can generate sufficient vibration to be sensed by the sensing member. The diversion piece 1 fits the radian of the pipe orifice and is installed at the pipe orifice. The spring piece 3 of the receiving baffle is used to receive vibration and transmit it to the optical cable, and is installed at a certain distance below the collection small hole 2 of the diversion piece 1. The buckle 4 is used to fix the optical cable. The sensing optical fiber (optical cable) is optically connected to the sensing member. The buckle 4 is located on one side or the middle part of the spring piece 3. The principle is that after the optical fiber is strained, internal changing Rayleigh scattering occurs, and the strain intensity value of the optical fiber is obtained by using the interference method. The signal processor 7 includes a special chip for processing and demodulating the optical modulation signal and an industrial computer (computer) for general digital signal processing. The laser 5 is the light source of the optical fiber sensor, which provides coherent light and injects it into the optical cable. The optical splitter 6 is used to interfere the transmitted laser and the backscattered light in the optical cable in the optical path, and the phase data is obtained through the demodulation chip in the signal processor 7, and the current device state and data result are displayed on the display after calculation. This device selectively enhances and receives the vibration signal of the discharge water flow at the drain outlet. At the same time, through a unique optical cable coiling method, the problem of monitoring small-flow discharge outlets is solved. This device adopts a discharge water flow enhancement member to fully collect the water flow and maximally convert the gravitational potential energy of water into kinetic energy, and the water flow velocity is increased. According to the calculation formula of the Reynolds number , the Reynolds number is proportional to the velocity. After the Reynolds number increases, the fluid flow becomes less stable. Small changes in the flow velocity are likely to develop and intensify, forming turbulence, and the fluid itself has relatively large vibrations. A vibration receiving baffle is used to receive the vibrations of the fluid and transmit them to the optical cable. Then, a relatively large vibration intensity is detected at the DAS end. Moreover, the optical cable uses a new layout method at the drain outlet, and its length is at least two spatial resolution sizes, solving the coupling problem between the drain outlet emission signal and the in-pipe flow signal. As Figure 3 shown, the layout is divided into two types: at the drain outlet of type I, the optical cable is wound around the pipe orifice, and the vibration signal of the drain pipe caused by the drainage at the pipe orifice can be received; for type II, the redundant optical cable is wound around both sides of the drain outlet, which is suitable for situations where the drain outlet is particularly large. During the layout process, the installation of the flow deflector 1 can be selected. When the water volume is small enough, an additional flow deflector 1 is installed to enhance the signal, solving the problem that the traditional drainage detection layout method based on optical fiber sensing cannot accurately sense low head and low flow rate drainage.

[0024] Please refer to Figures 4 to 7 , in the second aspect, the present invention also provides a method for decoupling and sensitivity enhancement of drainage perception using distributed optical fiber sensing, which is applied to the device for decoupling and sensitivity enhancement of drainage perception using distributed optical fiber sensing as described in the first aspect above, and includes the following steps: S1 Set the substrate parameters of the sensing element; In the embodiment of the present invention, the basic parameters include the sampling rate, spatial resolution, channel spacing, number of sampling points, and the duration to be collected.

[0025] Among them, the setting of the acquisition rate is restricted by the Nyquist sampling theorem and the highest vibration frequency in the current sampling environment, and it is better that there is no obvious over-π data in the system after setting. The spatial resolution and channel spacing define the density of the sensors in space. In this device, in order to maximize the decoupling effect, the set spatial resolution and channel spacing are the best values that the current device can achieve (the smaller the two values, the better). The required number of sampling points is calculated based on the length of the optical cable and the channel spacing (number of sampling points = length of the optical cable to be measured / channel spacing), and the number of sampling points needs to cover the entire length of the optical cable to be detected. The acquisition duration is based on the actual duration of the test and can collect the entire test experiment process completely. After the project commissioning is completed, the data acquisition will continue without interruption. After the basic parameters of the device are set, the entire system is tested (including whether the data network is connected, whether the file recording is normal, etc.) to ensure that the entire system starts to run.

[0026] S2 The sensing element calculates and processes the acquired signal to obtain differential phase data; Specific method: S21 The sensing element synchronizes the acquired signal to obtain processed data; S22 obtains differential phase data by calculating the difference between the phase data at adjacent moments of the processed data.

[0027] In the embodiment of the present invention, this step helps to eliminate static noise and environmental interference and highlight the dynamic changes in the signal.

[0028] Differential phase The calculation formula is: , where is the phase at time t, is the time difference between adjacent moments.

[0029] The specific process of obtaining the differential phase is as follows: The current signal output by any one path in the photoelectric detection module can be expressed as shown in the following formula: where represents the field strength of the light emitted by the laser 5, represents the initial time, represents the Rayleigh scattering coefficient of the optical effect, represents the beat frequency, is the laser phase signal output by the laser 5, represents the change in the phase of the measured optical fiber caused by the vibration of the external signal, represents the phase noise of the laser 5. After the Hilbert transform of Equation (1), the beat frequency signal will be added with a 90° phase shift and can be expressed as the following Equation (2): According to the above two formulas, the phase signal and the intensity signal can be obtained respectively as follows: After adopting polarization diversity reception, the final phase signal needs to add the phases of the two optical signals (P light, S light): where , are the phase sums of the P light and the S light after the nth group of samplings respectively. Next, the phase difference between two adjacent groups of data is obtained to represent the magnitude of its phase change amount, and its expression is as follows: S3 performs integral filtering processing on the differential phase data to obtain filtered data; In the embodiments of the present invention, it is necessary to integrate differential phase (strain rate) data to obtain strain data, and a filter is required to filter out the interference of low-frequency noise in the strain data. The device noise existing in the sensing element itself is in the low-frequency band less than 1 Hz. At the same time, temperature drift needs to be removed during data acquisition. Select a suitable type of high-pass filter according to specific application requirements, such as Butterworth high-pass filter, to reduce the low-frequency noise components and temperature drift in the signal.

[0030] S4 Calculate the vibration intensity based on the time window for the filtered data; In the embodiments of the present invention, select the time period when the drainage test occurs and calculate the vibration intensity (RMS). Its calculation method is to square first, then average, and then take the square root. The calculation formula is as follows: Where, is the strain amplitude of each sampling, N is the number of samplings within the time window, is the calculated RMS, that is, the vibration intensity.

[0031] In particular, this calculation process is a process of directly calculating RMS under the condition of no other environmental vibration interference. In the presence of other interfering vibrations, it is necessary to remove the interference according to the interference characteristics before calculating the vibration intensity.

[0032] S5 Obtain the vibration intensity value of the pipe orifice discharge based on the flow calibration result.

[0033] In the embodiments of the present invention, the calculation result of step S4 is an array of vibration intensities [RMS1, RMS2,...], and the calibration result is the actual position (index) of the signal at the drain outlet in the array. According to the index, the vibration intensity of the pipe orifice in the array can be obtained.

[0034] The method for obtaining the flow calibration result: S51 Build an equal-size model of the drain pipe orifice; In the embodiments of the present invention, the vibration signal intensity is affected by the pipe orifice drop, pipe orifice size, the layout size of the guide vane 1 and the receiving baffle. Therefore, it is necessary to build a drain pipe orifice model in a quiet laboratory with similar above parameters to the on-site environment; S52 Change the water flow rate based on the equal-size model to obtain the corresponding vibration intensity sensed by the optical cable at the pipe orifice; In the embodiments of the present invention, a water source with a stable flow rate of adjustable size is used to change the water flow rate, and a flowmeter is used to obtain the flow rate value during the experiment. By simulating the stable discharge of water from the drain outlet, the corresponding vibration intensity (RMS) is calculated using the above DAS sensing signal data acquisition process.

[0035] S53 Plot a scatter diagram based on the positive correlation between the vibration intensity and the water flow range; In the embodiment of the present invention, there is a positive correlation between the vibration intensity and the water flow range. The vibration intensity that can be specifically sensed is affected by DAS devices, cable sensitivity, pipe orifice head differences, etc. Therefore, there are still unknown parameters in the function that need to be determined through experimental data here.

[0036] S54 Use the least squares method to fit the parametric function; In the embodiment of the present invention, the mapping data of the obtained vibration intensity and water flow is used to establish a fitting function. Among them, the fitting method can use the least squares method to complete the determination of the best unknown parameters. In this example, the equation is used: , where RMS is the vibration intensity, v is the water flow, and a is the unknown parameter to be determined.

[0037] S55 Convert the parametric function to obtain the inverse function, and calculate the corresponding water flow to obtain the calibration result.

[0038] In the embodiment of the present invention, the independent variable and the dependent variable of the parametric function are converted to obtain the corresponding inverse function.

[0039] The inverse function is: ; The parameters have been determined in the previous step. Therefore, after obtaining the RMS of the corresponding pipe orifice each time using the DAS sensing data acquisition process, the corresponding water flow v can be calculated using this inverse function.

[0040] What is disclosed above is only the preferred embodiment of the drainage sensing decoupling and sensitivity enhancement device and method of the distributed optical fiber sensing of the present invention. Of course, the scope of the rights of the present invention cannot be limited by this. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A drainage sensing decoupling and sensitivity enhancement device for distributed optical fiber sensing, characterized in that it includes a discharge water flow enhancement member and a sensing member. The discharge water flow enhancement member includes a diversion sheet and a receiving baffle. The diversion sheet has collection small holes, and the collection small holes are located on one side of the diversion sheet. The receiving baffle is arranged on one side of the diversion sheet. The receiving baffle includes an elastic sheet and a buckle. The elastic sheet is arranged on one side of the diversion sheet, and the buckle is fixedly connected to the elastic sheet and is located on one side of the elastic sheet; the sensing member includes a laser, a splitter, a signal processor and a display, and the laser, the splitter, the signal processor and the display are connected in sequence.

2. A method for decoupling drainage sensing and enhancing sensitivity of distributed optical fiber sensing, applied to the device for decoupling drainage sensing and enhancing sensitivity of distributed optical fiber sensing as described in claim 1, characterized in that, It includes the following steps: Set the substrate parameters of the sensing member; The sensing member calculates and processes the collected signal to obtain differential phase data; Perform integral filtering processing on the differential phase data to obtain filtered data; Calculate the vibration intensity based on the time window for the filtered data; Obtain the vibration intensity value of the pipe orifice discharge based on the flow calibration result.

3. The drainage sensing decoupling and sensitivity enhancement method for distributed optical fiber sensing according to claim 2, characterized in that the basic parameters include sampling rate, spatial resolution, channel spacing, number of sampling points and duration to be collected.

4. The drainage sensing decoupling and sensitivity enhancement method for distributed optical fiber sensing according to claim 2, characterized in that the specific way for the sensing member to calculate and process the collected signal to obtain differential phase data: The sensing member performs synchronous processing on the collected signal to obtain processed data; Obtain differential phase data by calculating the difference between the phase data at adjacent moments of the processed data.

5. The drainage sensing decoupling and sensitivity enhancement method for distributed optical fiber sensing according to claim 2, characterized in that the method for obtaining the flow calibration result: Build an equal-size model of the drainage pipe orifice; Based on the equal-size model, change the water flow rate to obtain the corresponding vibration intensity sensed by the optical cable at the pipe orifice; Draw a scatter plot based on the positive correlation between the vibration intensity and the water flow rate; Use the least squares method to fit a parametric function; Convert the parametric function to obtain an inverse function, and calculate the corresponding water flow rate to obtain the calibration result.

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